Background. In recent years disposable ‘biodegradable bags’ have substituted a large number of conventional polymer bags. Most commercially available bags are made of cheap thermoplastic materials (polyethylene, polypropylene), which have good mechanical properties, but are non-biodegradable. In order to improve the biodegradability of bags synthetic polymers are usually mixed with natural polymers, such as starch or pro-oxidants. However, the essential question whether biodegradable bags are really eco-friendly and can be decomposed by microorganisms in the environment has not been answered yet. The aim of the study was to determine the biodegrad­ability of commercially available disposable bags.

Material and methods. Three different plastic bags (polyethylene, polyethylene oxy-biode­gradable, polyethylene biodegradable with addition of starch) and one paper bag were used in the study. Biodegradation of the bags was studied for 12 months in the soil environment (both with or without addition of the microbial agent). The efficiency of material biodegradation was assessed periodically using three different methods: CO2 evolution test, mechanical properties analysis and biofilm formation analysis.

Results. The results suggest that only paper bags are completely biodegradable in the soil envir­onment, as could be seen by their high mineralisation, deterioration of mechanical properties and formation of a bacterial biofilm on cellulose fibres. Polyethylene bags with the addition of starch were biodegradable, but to a lesser extent. Other bags were resistant to microbial degradation in soil. The addition of the microbial agent did not influence biodegradability of the bags under study.

Conclusions. The so-called ‘biodegradable’ plastic bags under study could not be bioavailable to autochthonous microorganisms inhabiting soil. Although they are described as ‘biodegradable’ on their labels, they may not be as eco-friendly as their manufacturers declare. Therefore, it is important to develop new, biodegradable polymer materials that can be used for production of commercially available bags.